A type of an X-ray irradiator including an X-ray tube, a high-voltage power supply, and a power supply for lighting a filament is most widely used among various types of X-ray irradiators. A high voltage of 10 kV to 500 kV depending on use is applied to the X-ray tube. Once the filament is lit, thermal electrons are emitted from a cathode part of the X-ray tube. The thermal electrons are accelerated by the high voltage, and thus collide against an opposed anode part. An X-ray is generated from energy produced by this collision. In the conventional X-ray generators, the X-ray tube and the high-voltage power supply, which is placed outside the X-ray tube, are connected with connectors. In the case of the connectors used for a high voltage, a sufficient creepage distance needs to be secured to prevent the discharge. For instance, when the voltage is 50 kV, 100 kV, or 200 kV, the connectors need to be as large as approximately 100 mm, 200 mm or 300 mm, respectively. Thus, it has been difficult to deal with these connectors.
With this taken into consideration, as shown in FIG. 8, a growing number of X-ray irradiators 1X have employed a configuration termed as a mono-block or mono-tank configuration in which an X-ray tube 11 and a high-voltage generator 2X are placed in the casing 18 filled with an insulation oil 13 or an insulation resin.
An X-ray irradiator 1X of this type uses the X-ray tube 11, which is called a neutral grounded type. The X-ray irradiator 1X or the like for checking the quality of IC chips or cast products is used with a voltage of 160 KV in total applied between an X-ray tube anode 14 and an X-ray tube cathode 15, that is, with 80 kV applied to the anode 14 and −80 kV applied to the cathode 15. There are various other voltage application methods for the X-ray tube 11, such as: the X-ray irradiator 1X in which different voltages are applied; the X-ray irradiator 1X in which a positive high-voltage is applied to the anode 14 while the electric potential of the cathode 15 is kept at zero; and the X-ray irradiator 1X in which a negative high-voltage is applied to the cathode 15 while the electric potential of the anode 14 is kept at zero.
The X-ray tube 11 emits scattered X-rays, which are produced inside the X-ray tube 11, from not only an X-ray irradiation window 17 but also every peripheral part of the X-ray tube 11. For this reason, the X-ray tube 11 is encircled with an insulation cylinder 32, and moreover, is encircled with an X-ray shielding member 16 on top thereof. The X-ray shielding member 16 uses lead in many cases. The X-ray shielding member 16 is fixed at zero electric potential, namely an earth potential. The X-ray irradiation window 17, provided to the X-ray tube 11 by removing a part of the X-ray shielding member 16, is a portion through which an X-ray is emitted to the outside of the X-ray tube 11. The X-ray irradiation window 17 uses beryllium or the like, which is excellent in X-ray transmission property.
In addition, the insulation oil 13 in the X-ray irradiator 1X is used for insulation from the high voltage, and for discharge of heat, which is generated from the X-ray tube 11, to the outside of the X-ray irradiator 1X through conduction of the heat to the casing 18 by convection (see Patent Document 1, for instance).
The high-voltage generator 2X, which employs a voltage generating transformer for generating several kV and multiple connected Cockcroft-Walton circuits 23 shown in FIG. 6A, is used in many cases. In each Cockcroft-Walton circuit 23, capacitors 24 and diodes 25 are arranged in a ladder-like manner. Thus, the Cockcroft-Walton circuit 23 has a function of generating a direct-current high voltage with application of an alternating-current voltage VAC, by amplifying the applied voltage VAC approximately twice to twenty times due to both the charging effects of the capacitors 24 and the rectifying effects of the diodes 25.
Patent Document 1: Japanese Patent Application Kokai Publication No. 2007-26800.